When upgrading Ubuntu (and probably other *nixes), the upgrade process will show a diff of changed configuration files and ask whether I'd like to replace them, keep the old version, or manually merge them. I couldn't find any such programs with Google or searching through the Ubuntu packaging documentation. Do you know of any such programs which have the following features?

Few or no dependencies (ideally a single shell script).

Shell only (ideally without curses).

Does not try to be "clever," for example by automatically merging.

Edit: I've written this small thing to do some preliminary checks and ask the user what to do, but it's not very flexible or nice:

I'd much rather leverage version control. In fact, I wish Debian packages systematically checked the upstream versions into a branch and let me set up a merge policy. Etckeeper goes part of the way with version control for /etc, but it doesn't record upstream versions, which means you can't go merges.
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GillesNov 3 '11 at 22:45